He dragged her into the basement, tied her up and rubbed vervain on her. Stefan wanted answers! Using a series of flashbacks, here is what Katherine revealed:
- She made a deal with George Lockwood in 1864 that she'd help him round up the 27 vampires in Mystic Falls and burn them in the church. But he'd help her slip out and escape.
- In exchange for freeing Katherine, and keeping it a mystery, George received a gift: the moon stone Mason is now searching for and which Tyler possesses.
- Before Katherine left Mystic Falls, she found Damon and Stefan dead (remember, their father shot them when they tried to help Katherine escape after she was initially apprehended) and whispered to Stefan that she loved him.
Might Katherine really be telling the truth that she came back to town for Stefan? He seemed disturbed during the episode when she said she never compelled his love.
Meanwhile, Caroline spent the hour trying to keep Elena away from Stefan, as they spent the day at a barbecue hosted by Jenna (that also included Damon, Alaric and Mason) and also trying to convince her that it would never work between a human and a vampire. Once Elena did make it to Stefan's, she came face to face with Katherine (who escaped the basement because she was faking it all along, she's trained herself to be unaffected by vervain), who taunted Elena briefly before vanishing.
After this rough day, Stefan and Elena went for dinner at Mystic Grill. They spoke as if they were breaking up because Katherine's presence made things too difficult/dangerous, as Elena left in tears. But we later learned it was all a ploy: Caroline was listening in to the fake break-up and Stefan/Elena now know she's working with Katherine, which viewers saw earlier in the hour; Katherine had told Caroline to keep Elena away from Stefan all day and force feed her ideas for a break-up.
Damon also overheard the conversation. He had a tough day, too, trying to kill Mason Lockwood with silver, only to learn that werewolves can't actually be killed with metal. As Mason told Damon afterwards, he's now made an enemy.
Source: TV Fanatic